1. Field of the Invention
The present invention relates to a light-resistant dispersant, and more particularly, to an ultraviolet (UV) light absorbing dispersant and an ink composition containing the same.
2. Description of the Related Art
In general, ink compositions for ink-jet printing contain a colorant, a solvent, and an additive, such as a dispersant. A dye or a pigment may be used for the colorant. However, when a dye is used as the colorant, water resistance and light resistance are limited, whereas when a pigment is used as the colorant, water resistance and light resistance are improved.
A common dispersant used in ink compositions is a polymer dispersant bearing hydrophilic and hydrophobic groups. The hydrophobic group of the polymer dispersant interacts with a colorant in the ink composition to stabilize dispersion of the colorant. The hydrophilic group of the polymer dispersant interacts with an aqueous solvent to offer steric stability.
However, due to the large molecular weight of the polymer dispersant, the physical properties, for example, the viscosity, of the composition are greatly varied even when there is a minor change in the amount of the dispersant. Accordingly, it is difficult to adjust the amount of the additive used. In addition, although the polymer dispersant includes hydrophilic groups in its molecular structure, the hydrophilic fraction of the polymer with respect to the total amount of the composition is too small to sufficiently dissolve the compound in water, and it takes more time to dissolve the hydrophilic fraction of the polymer.
After printing on media, such as paper, using the ink composition, the ink printed on the media is exposed to the air, moisture, and/or sunlight. Accordingly, an ink composition having effective light resistance and water resistance in such environments is required.
To improve the light resistance of ink compositions, a method of adding a silicon-containing compound as a light-resistant additive to offer a UV absorbing effect is suggested in U.S. Pat. No. 6,346,595. However, this silicone-containing compound is structurally complex, and thus has poor miscibility with other components of the ink composition, especially when it has a larger molecular weight.